EXTEENAL CHAEACTEES AND HABITS 73
Bennett (176), in describing the habits of the Siamang, states: " He invariably walks Sin the erect posture when on a level surface; and then the arms either hang down, enabling him to assist himself with his knuckles; or what is more usual, he keeps his arms uplifted in nearly an erect position, with the hands pendent ready to seize a rope, and climb up on the approach of danger or on the obtrusion of strangers. He walks rather quick in the erect posture, with a waddling gait, and is soon run down if, whilst pursued, he has no opportunity of escaping by climbing. TVhen he walks in the erect posture he turns the leg and foot outwards, which occasions him to have a waddling gait and to seem bow-legged." Sometimes they progress by leaps, rather than by placing one foot in front of the other. The whole of the narrow foot is placed on the ground and raised without elasticity of step.
Classification and Distribution.—The family Hylobatidse includes two genera—Symplialangus and Hylobates. The former contains one animal, the Siamang, and the latter includes all other Gibbons.
The Siamang (S. syndactylus) is found in Sumatra. It is the largest Gibbon, and it is the only one possessing air-sacs communicating with the larynx. The fur is black and glistening, and its colour is not relieved by a circumfacial band of white hairs. The second and third toes are connected by a web for more than half their length, hence the name tk syn dactyl us/5 The animals constituting the genus Hylobates are found in Further India, the Malay Archipelago, Hainan and Southern China. It is not known exactly how many species exist, and the multiplication of synonyms has led to much